Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$64.55	10.367%	$71.2419	$71.24	$71.25	$71.20
Purchase #2	$150.27	5.321%	$158.2659	$158.27	$158.25	$158.30
Purchase #3	$23.47	6.589%	$25.0164	$25.02	$25.00	$25.00
Purchase #4	$29.56	10.354%	$32.6206	$32.62	$32.60	$32.60
Purchase #5	$40.73	10.196%	$44.8828	$44.88	$44.90	$44.90
Purchase #6	$147.77	3.760%	$153.3262	$153.33	$153.35	$153.30
Purchase #7	$72.92	5.669%	$77.0538	$77.05	$77.05	$77.10
7 purchase totals =	$529.27		$562.4076	$562.41	$562.40	$562.40